Process for preparing anhydride polymers

Abstract

A process for preparing anhydride polymers in aromatic hydrocarbon solvents using a dialkyl peroxide/amine compound initiator system is disclosed. The amine compound allows more efficient use of free-radical initiators while achieving high monomer conversion polymerizations compared to conventional initiator systems, particularly in the preparation of maleic anhydride polymers.

We claim: 
     
       1. A polymerization process for preparing anhydride polymers, comprising polymerizing monomer selected from one or more of maleic anhydride, citraconic anhydride, itaconic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, bicyclo[2.2.2]-5-octene-2,3-dicarboxylic anhydride, 3-methyl-1,2,6-tetrahydrophthalic anhydride and 2-methyl-1,3,6-tetrahydrophthalic anhydride, in the presence of (a) an aromatic hydrocarbon,   (b) 3 to 30 percent by weight, based on weight of monomer, of dialkyl peroxide, and   (c) 0.01 to 3 percent by weight, based on weight of monomer, of an amine compound selected from one or more of ammonia, (C 1  -C 22 )aliphatic amine and (C 6  -C 20 )aromatic amine;   until greater than 90 percent by weight of the anhydride monomer has been converted to polymer.   
     
     
       2. The process according to claim 1 wherein the polymerization is conducted at a temperature from 80 to 180° C. 
     
     
       3. The process according to claim 1 wherein the monomer comprises at least 90 percent maleic anhydride by weight based on total weight of monomer. 
     
     
       4. The process according to claim 1 wherein the aromatic hydrocarbon is selected from one or more of toluene, (C 8 )aromatic hydrocarbon, (C 9 )aromatic hydrocarbon and (C 10 )aromatic hydrocarbon. 
     
     
       5. The process according to claim 4 wherein the (C 8 )aromatic hydrocarbon is selected from one or more of ethylbenzene, ortho-xylene, meta-xylene and paraxylene. 
     
     
       6. The process according to claim 1 wherein the amine compound is selected from one or more of dibutylamine, ethylhexylamine, methydibutyl-amine, ethylenediamine, diethylenetriamine, n-octylamine, 1,1,3,3-tetramethylbutylamine and dimethylaniline. 
     
     
       7. The process according to claim 1 wherein the dialkyl peroxide is used in an amount from 10 to 20 percent by weight based on weight of monomer. 
     
     
       8. The process according to claim 1 wherein the amine compound is used in an amount from 0.1 to 1 percent by weight based on weight of monomer. 
     
     
       9. The process according to claim 1 wherein the anhydride polymer has a weight-average molecular weight of less than 2,000. 
     
     
       10. The process according to claim 1 wherein the anhydride is present in a concentration of from 25 to 70 percent by weight, based on total weight of reaction mixture. 
     
     
       11. The process according to claim 10 wherein the concentration is from 30 to 60 percent by weight. 
     
     
       12. The process according to claim 1 wherein optional monomer polymerized in combination with anhydride monomers is less than 20 percent by weight, based on total weight of monomer. 
     
     
       13. The process according to claim 12 wherein the optional monomer polymerized is less than 5 percent by weight. 
     
     
       14. The process according to claim 1 wherein greater than 95 percent by weight of the anhydride monomer has been converted to polymer. 
     
     
       15. The process according to claim 1 wherein the amine compound and the dialkyl peroxide are in a weight ratio of 0.001/1 to 0.5/1 with respect to each other. 
     
     
       16. The process according to claim 1 wherein the dialkyl peroxide is selected from one or more of di-tert-butyl peroxide, di-tert-amyl peroxide, n-butyl-4,4-di(tert-butylperoxy)pivalate, tert-butyl cumyl peroxide and dicumyl peroxide.